This invention relates to the class of solar collectors known as central receiver collectors, in which a plurality of mirrors reflect solar radiation onto a radiation receiver having dimensions small compared to the dimensions of the mirror field. Various design proposals for central receiver collectors dominate the current effort to achieve practical large scale solar power plants. The design proposals for large scale collectors generally call for independently aimed and actuated heliostats, with control signals coming either from a control computer or from a combination of computer for coarse control and an optical sensor associated with each individual heliostat for fine control.
Previously known collective control systems using linked mirrors, such as described by Francia in U.S. Pat. No. 3,466,119, have been dismissed as impractical for use in large scale collectors. In a more recent U.S. Pat. No. 4,102,326, incorporated herein for reference, there is described a rigid mechanical linkage system for controlling the mirrors of a central receiver collector. However, while the rigid mechanical linkage should be useful for collectors from quite small size up to fairly substantial installations, it also would not be readily adaptable to very large scale collectors.
However, there appears to be the need for some sort of collectivization of the heliostat control for large scale systems. The current design concepts, using independently aimed mirrors, call for either individual mirrors which are as large as could possibly be accommodated by the size of the radiation receiver chosen for the large scale collector, or for groups of mirrors in individual structures of equivalent size. As the amount of structural material required to construct a heliostat of adequate rigidity will vary roughly as the cube of the linear dimensions of the mirror structure, it would be advantageous from the standpoint of material utilization if smaller individual mirror structures could be made economically practical. A further advantage which would appear to be inherent in the use of a larger number of individually smaller heliostats than are called for in the existing central receiver concept proposals is that manufacturing economies of scale could be more readily obtained. However, for the advantages which appear to be associated with the use of smaller individual heliostats to be realized, it would apparently be required that an effective collective control system usable in very large scale collectors be developed, in order to reduce the cost for guidance and control of each heliostat.